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brmadhukar
Joined: 21 Jun 2002
Posts: 844
Helped: 29
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 10 Feb 2003 14:52 PCB considerations for filter |
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Hi,
At what frequencies (for 2,4,6,8 layer boards) can I start considering the layout or placement for passive band pass filters, or do component values dictate the placement.
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brmadhukar
Joined: 21 Jun 2002
Posts: 844
Helped: 29
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| 10 Feb 2003 16:23 |
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Hi,
I also need to switch the bandwiths of the filters. What is the best way to do this. Is it mechanical (provide jumpers) or can I use analog switches. If I use analog switches should I consider any specific for say 15MHz filter.
TIA
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flatulent
Joined: 19 Jul 2002
Posts: 4859
Helped: 287
Location: Middle Earth
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| 10 Feb 2003 18:03 line lengths |
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The trace lengths compared to a wave length is the criteria. This ratio should be very small. Also the inductive coupling between inductors should be minimized. This is done by laying out so they are not near each other and have their axis at right angles to the nearest one.
As far as switching values, it depends upon the paasitic on resistance and off capacitance of the switches. Are you going to set the filter once for the life of the circuit or several times? If once, just load the prpoer part values. If several times, use solder jumpers.
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